Monsanto still doesn't know how Roundup Ready wheat volunteers showed up in a summer fallow field in Oregon this spring.

The company has tested the foundation seed of the wheat varieties planted in that field, as well as foundation seed representing some 60 percent of the varieties grown in Oregon and Washington, and found no evidence of contamination.

Robb Fraley, Monsanto's chief technology officer, said he doesn't know what kind of tests USDA and Oregon State University have used, and that only a PCR test Monsanto has developed can precisely identify the Roundup Ready wheat trait. Fraley also said the seed used by the Oregon farmer could have been contaminated, accidentally or purposefully.

"You know, we don't know yet. All we can tell you is that it's isolated and it could have been either accidental or purposeful." Fraley emphasizes this is an isolated case. "That really helps us focus on what our next steps should be and that it's not widespread."